Tropical Storm LESLIE

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TROPICAL STORM LESLIE DISCUSSION NUMBER 41
NWS NATIONAL HURRICANE CENTER MIAMI FL AL122012
1100 AM AST SUN SEP 09 2012
LESLIE HAS A VERY BROAD EYE AS EVIDENCED BY BERMUDA RADAR
OBSERVATIONS AND SATELLITE IMAGES. A RECENT ASCAT PASS OVER THE
TROPICAL CYCLONE SHOWED 40-45 KT WINDS...AND ENHANCED IR DATA SHOWED
SOME INCREASE IN THE DEEP CONVECTION IN CLUSTERS SURROUNDING THE
CENTER. THE CURRENT INTENSITY IS HELD AT 50 KT FOR THIS ADVISORY.
SINCE LESLIE LACKS A WELL-DEFINED INNER CORE...IT MAY HAVE
DIFFICULTY RE-INTENSIFYING AS IT MOVES FARTHER AWAY FROM THE COOLER
WATERS IT UPWELLED. HOWEVER...UPPER-TROPOSPHERIC WINDS ARE
FORECAST TO BE FAVORABLE FOR STRENGTHENING DURING THE NEXT DAY OR
SO...AND THE OFFICIAL WIND SPEED FORECAST SHOWS THE CYCLONE
REGAINING HURRICANE STATUS AS IN THE PREVIOUS ADVISORY. THIS IS
ALSO IN GOOD AGREEMENT WITH THE LATEST LGEM GUIDANCE. BEYOND 48
HOURS...THE GLOBAL MODELS DEPICT LESLIE TO BE QUITE DEEP BUT
BECOMING EMBEDDED WITHIN A FRONTAL ZONE...SO THE SYSTEM IS FORECAST
TO BECOME A VIGOROUS EXTRATROPICAL CYCLONE IN 2-3 DAYS AS IT MOVES
OVER THE ATLANTIC. BY DAY 5 THE SYSTEM IS LIKELY TO MERGE WITH A
LARGE LOW TO THE NORTHWEST OF SCANDANAVIA.
LESLIE IS BEGINNING TO INCREASE ITS FORWARD SPEED...AND THE INTIAL
MOTION IS ESTIMATED TO BE 010/9. AS A MID-TROPOSPHERIC TROUGH
MOVES OFF THE NORTHEAST U.S. COAST...THE CYCLONE IS EXPECTED TO
ACCELERATE NORTH-NORTHEASTWARD IN THE FLOW ON THE EAST SIDE OF THE
TROUGH OVER THE NEXT COUPLE OF DAYS. IN 3-4 DAYS...THE POST-
TROPICAL CYCLONE SHOULD TURN EAST-NORTHEASTWARD IN THE HIGHER
LATITUDE WESTERLIES. THE OFFICIAL TRACK FORECAST IS SOMEWHAT
FASTER THAN THE PREVIOUS ONE IN THE LATTER PART OF THE FORECAST
PERIOD...BUT NOT AS FAST AS THE LATEST GFS SOLUTION.
LONG-PERIOD SWELLS FROM LESLIE ARE EXPECTED TO PRODUCE ROUGH SURF
AND LIFE-THREATENING RIP CURRENTS ON BERMUDA AND ALONG MUCH OF THE
U.S. EAST COAST FOR THE NEXT FEW DAYS.
FORECAST POSITIONS AND MAX WINDS
INIT 09/1500Z 32.0N 62.4W 50 KT 60 MPH
12H 10/0000Z 33.6N 62.0W 55 KT 65 MPH
24H 10/1200Z 36.3N 60.9W 60 KT 70 MPH
36H 11/0000Z 40.2N 59.0W 65 KT 75 MPH
48H 11/1200Z 46.5N 55.5W 65 KT 75 MPH
72H 12/1200Z 58.0N 42.0W 65 KT 75 MPH...POST-TROP/EXTRATROP
96H 13/1200Z 62.0N 20.0W 55 KT 65 MPH...POST-TROP/EXTRATROP
120H 14/1200Z...MERGED
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FORECASTER PASCH
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